The main feature of this line is the unique rack system and the equally unique and complicated locomotives. To quote from Sir Guilford L. Molesworths report of 1886: The locomotive used for working on the Abt System has two distinct functions: first, that of traction by adhesion as in an ordinary loco and second, that of traction by pinions acting upon the rack bars.

The brakes are four in number-two hand brakes action by friction and two acting by preventing the free escape of air from cylinder and thus using compressed air in retarding the progress of the engine. The former are used for shunting whilst the latter for descending steep gradients. One of the hand brakes acts on the tyres of the wheels in the ordinary manner and the second acts on grooved surfaces of the pinion axle but can be used in those places where the rack is laid. Even after hundred years, the brake system on Nilgiri locomotives is as intricate and cumbersome as it was in 1886.

The train journey from Chennai to Metupalaiyam then took just over 17 hours and cost Rs 20 first class and another 20 rupees to cover the remaining 33 miles up the steep mountain road to Coonoor and Ootacamund by the Nilgiri carrying Companys Mail and Express Tonga Service while heavy baggage had to be sent bullock cart. The only alternative was to hire a pony and arrange for luggage to be taken up by individual baggage carriers using the shorter but even steeper old road to Coonoor.

Nowadays, the traveller from Ootacamund leaves Chennai central station on the evening Nilgiri Express at 9.00 p.m. and arrives at Mettupalaiyam at 7.10 am. After a 10 hour journey. There he merely crosses the platform to join the metre gauge train which leaves at 7.25 am. And reaches Udagamandalam at 11.40 a.m. in less than 15 hours. The Nilgiri Railway (NMR) is a feat of engineering unique in the east.

The line is a metre gauge, practically level for the first four and a half miles, to Kallar at the immediate foot of the hills. As soon as the train leaves Kallar, the rack rails appears and the long climb begins. In the next 12 miles to Coonoor, the line rises 4,363 feet curving almost continuously as it clings to the mountainside, crossing lofty viaducts or tunnels, the longest being 317 feet in length. The gradient posts read one in twelve and a half with monotonous consistency.

Construction expenses were heavy because in addition to the tunnels, a big bridge over the river bhawani at the foothills was necessary. Besides this large bridge, 26 other bridges smaller in size, were constructed and heavy expenditure incurred in rock-cutting and blasting.

To quote a south Indian railway spokesman in 1935: those engineers must have been lovers of nature when they decided on the alignment.